Subsonic small-caliber ammunition and bullet used in same

ABSTRACT

A bullet comprises a casing engaging segment, a rifling leade mating segment, and a tip segment. The rifling leade mating segment has a frusto-conical shape tapering from a first diameter at a first end portion thereof to a second diameter at a second end portion thereof. The rifling leade mating segment extends from a first end portion of the casing engaging segment. The tip segment extends from the second end portion of the rifling leade mating segment. The first diameter is greater than the second diameter.

CROSS REFERENCE TO RELATED APPLICATIONS

This continuation-in-part patent application claims priority fromco-pending U.S. Non-provisional patent application having Ser. No.12/800,879, filed May 25, 2010, entitled “Subsonic Small-CaliberAmmunition And Bullet Used In Same”, having a common applicant herewithand being incorporated herein in its entirety by reference.

FIELD OF THE DISCLOSURE

The disclosures made herein relate generally to ammunition for firearmsand, more particularly, to subsonic ammunition for use with semi andfully automatic weapons.

BACKGROUND

The projectile (i.e., bullet) from a fired weapon, particularly a rifle,typically leaves the muzzle of the weapon at a speed that is greaterthan the speed of sound, i.e. a muzzle velocity of greater thanapproximately 1086 ft/sec. at sea level under standard conditions oftemperature and pressure. Such a speed is referred to as beingsupersonic. Causing the bullet to achieve supersonic speed isadvantageous because the faster a projectile travels, the flatter is itstrajectory to its intended target. Also, faster speeds of projectilestend to reduce the effects of lateral wind forces upon the path of theprojectile to its intended target.

Due to supersonic speed of a projectile enhancing its accuracy ofdelivery to an intended target, it can be seen why it is desirable forprojectiles to have a supersonic muzzle velocity. However, projectilestravelling at supersonic speeds generate an audible sound during theirfree flight, which can undesirably be used to locate the source of theweapon from which the projectile was fired. Under certain circumstancesof military operations and/or police operations, it is desirable thatthe source of the weapon firing a projectile not be identifiable by thesound generated by the travelling projectile. Furthermore, for aprojectile of a given shape and mass, it is sometimes desirable formuzzle velocity to be used in limiting the potential for the projectileto strike a down-range object in the case with the projectile misses orpasses through its intended target.

In certain situations, one approach for mitigating adverse concernsrelating to supersonic muzzle velocity is to restrict the speed oftravel of the projectile to a subsonic speed (i.e., a muzzle velocity ofless than approximately 1086 ft/sec. at sea level under standardconditions of temperature and pressure). In doing so, the projectiledoes not generate an audible sound during its free flight, thus limitingthe potential for locating the source of the projectile. Additionally,subsonic flight reduces the distance that a projectile can travel,thereby limiting the potential for the projectile to strike down-rangeobjects.

In semi-automatic and fully automatic weapons, pressure (i.e., energy)generated by firing of a round of ammunition serves to energize theweapon's bolt actuation mechanism. As such, implementing subsonic flightof a projectile in a manner that reduces pressure within a weapon'sbarrel bore can result in there being insufficient energy generatedduring combustion of the ammunition to cycle the bolt in asemi-automatic or fully-automatic weapon and/or to lock the bolt in itsopen position upon the firing of the last round in the weapons'magazine. In some cases, gas pressure provided at a gas port of a weaponcan be increased to suitable energizes a bolt-actuation mechanism of theweapon through use of a sound suppressor to sufficient levels. However,removal of the sound suppressor renders such weapon inoperable in itssemi-automatic and/or automatic modes of operation when suchpressure-deficient rounds of ammunition are used.

Accordingly, subsonic ammunition that is capable of providing sufficientenergy for cycling the bolt actuation mechanism of a semi-automatic orfully automatic weapon without the use of a sound suppressor isadvantageous, desirable and useful.

SUMMARY OF THE DISCLOSURE

Embodiments of the present invention are directed to bullets and roundsof ammunition that are configured for use with small-calibersemi-automatic and automatic weapons. More specifically, small-caliberbullets and rounds of ammunition configured in accordance withembodiments of the present invention provide subsonic flight whendischarged in a semi-automatic or fully-automatic weapon and providesufficient barrel bore pressure characteristics for cycling agas-energized bolt actuation mechanism of such semi-automatic orfully-automatic weapon without the use of a sound suppressor to augmentgas pressure within the barrel bore of the weapon. Ammunition configuredin accordance with the present invention is well suited for applicationswhere firepower is more of a consideration than is stealth. Accordingly,embodiments of the present invention advantageously overcome one or moreshortcomings associated with some conventional small-caliber subsonicrounds of ammunition.

In one embodiment of the present invention, a bullet comprises a casingengaging segment, a rifling leade mating segment, and a tip segment. Therifling leade mating segment has a frusto-conical shape tapering from afirst diameter at a first end portion thereof to a second diameter at asecond end portion thereof. The rifling leade mating segment extendsfrom the first end portion of the casing engaging segment. The tipsegment extends from the second end portion of the rifling leade matingsegment. The first diameter is greater than the second diameter.

In another embodiment of the present invention, a bullet comprises ajacket drawn from a copper alloy material and a lead core providedwithin the jacket. The jacket has a casing engaging segment, a riflingleade mating segment, and a tip segment. The rifling leade matingsegment linearly tapers from a first diameter at a first end portionthereof to a second diameter at a second end portion thereof. Therifling leade mating segment extends from the first end portion of thecasing engaging segment. The tip segment extends from the second endportion of the rifling leade mating segment. The first diameter isgreater than the second diameter. The casing engagement segment definesa bearing surface portion of the jacket. The bearing surface portion hasa nominal thickness less than about 0.010″. The copper alloy material ofat least the bearing surface portion of the jacket has a nominalhardness that is substantially greater than an as-drawn hardness of thecopper alloy material of the bearing surface portion of the jacket.

In another embodiment of the present invention, a round of ammunitionconfigured for providing sufficient energy for cycling a bolt carrier ina rifle having a gas-energized bolt carrier actuation mechanismcomprises a small-caliber cartridge casing configured in accordance withan original equipment manufacturer (OEM) specification for the rifle, abullet engaged within a bullet receiving opening of the small-calibercartridge casing thereby forming a propellant-receiving cavity withinthe small-caliber cartridge casing, and a propellant within thepropellant-receiving cavity of the small-caliber cartridge casing. Thebullet has a casing engaging segment, a rifling leade mating segment,and a tip segment. The rifling leade mating segment has a frusto-conicalshape tapering from a first diameter at a first end portion thereof to asecond diameter at a second end portion thereof. The rifling leademating segment extends from the first end portion of the casing engagingsegment. The tip segment extends from the second end portion of therifling leade mating segment. The first diameter is greater than thesecond diameter. The casing engagement segment defines a bearing surfaceportion of the bullet engaged within the bullet receiving opening of thesmall-caliber cartridge casing. The propellant is configured by amanufacturer thereof for being used in medium caliber ammunition.

These and other objects, embodiments, advantages and/or distinctions ofthe present invention will become readily apparent upon further reviewof the following specification, associated drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view showing a round of ammunition configured inaccordance with a first embodiment of the present invention.

FIG. 2 is a fragmentary cross-sectional view of the round of ammunitionof FIG. 1.

FIG. 3 is a fragmentary cross-sectional view of a round of ammunitionconfigured in accordance with a second embodiment of the presentinvention positioned within a mating chamber of a rifle barrel.

FIG. 4 is a side view showing a bullet of the round of ammunition shownin FIG. 3.

FIG. 5 is a fragmentary cross-sectional view of the rifle barrel shownin FIG. 3.

DETAILED DESCRIPTION OF THE DRAWING FIGURES

Referring now to FIGS. 1 and 2, a round of ammunition 100 configured inaccordance with the present invention is shown. The round of ammunition100 is configured for use with small-caliber semi-automatic andautomatic weapons (e.g., a rifle). Advantageously, the round ofammunition 100 is configured to provide subsonic flight when dischargedin a semi-automatic or fully-automatic weapon and to provide sufficientgas pressure characteristics for cycling a gas-energized bolt actuationmechanism of such semi-automatic or fully-automatic weapon without theuse of a sound suppressor to augment gas pressure. In doing so, theround of ammunition 100 advantageously overcomes a key shortcomingassociated with some conventional small-caliber subsonic rounds ofammunition.

The round of ammunition 100 includes a small-caliber cartridge casing102 configured in accordance with an original equipment manufacturer(OEM) specification for a weapon. The small-caliber cartridge casing 102includes a first end portion 104 and a second end portion 106.Typically, a primer is mounted within the second end portion 106 therebymaking the second end portion substantially closed. Preferably, but notnecessarily, the small-caliber cartridge casing 102 can be made a metalmaterial (e.g., brass) or from a polymeric material (e.g., nylon).

Standards for the shape and size of a cartridge for a certain weapons ofa given caliber have been established and published by one or morevarious entities and/or organizations. Examples of such entities and/ororganizations include, but are not limited to, Sporting Arms andAmmunition Manufacturers Institute (SAAMI), Permanent InternationalCommission for Firearms Testing (CIP), and North Atlantic TreatyOrganization (i.e., NATO). A rifle of the M4/M16/AR15 family of carbinerifles is a weapon that is capable of being operated in a semi-automaticmode and/or fully-automatic mode and that utilizes barrel bore pressureresulting from discharge of a round of ammunition to energize a boltactuation mechanism of the weapon. Thus, in one embodiment, the round ofammunition 100 can be configured for use with a rifle of the M4/M16/AR15family of carbine rifles. However, in view of the disclosures madeherein, it is disclosed that a skilled person will appreciate otherweapons for which a round of ammunition configured in accordance withthe present invention will be useful and that embodiments of the presentinvention are not unnecessarily limited to use with any particularweapon (i.e., any particular rifle, piston, or other type ofsmall-caliber firearm).

The round of ammunition 100 has a bullet 108 (i.e., a projectile) with abearing surface portion 110 engaged within a bullet receiving opening112 of the small-caliber cartridge casing 102. The bullet receivingopening 112 is located at the first end portion 104 of the small-calibercartridge casing 102. In this manner, a propellant-receiving cavity 114is formed within the small-caliber cartridge casing 102 between itsfirst and second end portions 104, 106. An ogive portion 116 (i.e.,contoured tip portion) of the bullet 108 extends beyond the bulletreceiving opening 112 and, optionally, some of the bearing surfaceportion can also extend beyond the bullet receiving opening 112.

As shown in FIG. 2, the bullet 108 has a core 118 made of a first typeof metal disposed within a core-receiving cavity 119 of a jacket 120made of a second type of metal. A jacket configured in accordance withthe present invention can be made by the process of drawing metal (e.g.,a sheet of metal) into a given shape and the bearing surface portion 110can have a thickness of less than about 0.010″. In a preferredembodiment, the bearing surface portion 110 has a nominal thicknessbetween about 0.004″ and about 0.008″. Preferably, but not necessarily,the jacket 120 is made from a copper alloy including about 90% copper(Cu) and up to about 10% zinc (Zn) and the core 118 is made from a metalhaving lead as its major constituent component. In a preferredembodiment, the jacket 120 is made from a copper alloy having a minimumof about 2% zinc.

It is disclosed herein that, in an alternate embodiment, the bullet 108can have a core that is formed to provide the intended exterior profileof the bullet 108 and have a plated jacket provided over the core. Insuch an alternate embodiment, the core is formed to have precisedimensions and profile of the bullet 108. The core is then plated usinga suitable plating process to form the jacket to have a thickness thatprovides the bullet with required/intended finished dimensions. Forexample, the core can be plated to provide the bullet 108 with anoutside diameter at the bearing surface portion 110 that is of arequired/intended dimension.

The bearing surface portion 110 and, optionally, the ogive portion 116have a nominal hardness that is substantially greater than an as-drawnhardness of the jacket 120. In a preferred embodiment, the jacket 120 isdrawn from a copper alloy material having a tensile strengthsubstantially below about 32 ksi. Subsequent to the jacket 120 beingdrawn and the core 118 being formed within the core-receiving cavity 119of the jacket 120, the bearing surface portion 110 and optionally theogive portion 116 are hardened to have a tensile strength greater thanabout 32 ksi. In a preferred embodiment, the bearing surface portion 110and optionally the ogive portion 116 are hardened to have a tensilestrength between about 32 ksi and about 44 ksi. Optionally, the finishedhardness specification for the copper alloy material can be specified asbetween about one-eighth hard and about one-half hard with respect tothe copper alloy material being “dead soft”. As such, it is disclosedherein that, after forming the core 118 within the core-receiving cavity119 of the jacket 120, the bearing surface portion 110 of the jacket 120and optionally the ogive portion 116 preferably have a nominal hardnessthat is substantially greater than an as-drawn hardness of the jacket120.

Examples of means for hardening the jacket 120 include, but are notlimited to, shot peening, ultrasonic hardening, and the like. In thecase where the jacket is shot peened, the jacket 120 and the shot (e.g.,steel shot) can optionally be exposed to a friction-reducing materialcomposition during such shot peening so that the shot peening causes atleast a portion of an exterior surface 122 of the jacket 120 to becomecoated with a layer of friction-reducing material composition.Molybdenum disulfide is one example of a friction-reducing materialcomposition (i.e., a lubricant) to which the jacket 120 and the shot(e.g., steel shot) can be exposed during such shot peening for causingthe exterior surface of the jacket 120 to become coated with a layer offriction-reducing material composition (i.e., a layer of molybdenumdisulfide).

As shown in FIG. 2, the round of ammunition 100 has a propellant 124(e.g., powder) within the propellant-receiving cavity 114. Thepropellant 124 can be a relatively slow burning type propellant thatprovides a rapid peak in pressure build up within thepropellant-receiving cavity 114 and that maintains a broader burnduration than relatively fast burning type propellants. In oneembodiment, the propellant 124 is configured by a manufacturer thereoffor being used as a medium caliber ammunition propellant. One example ofsuch a medium caliber propellant suitable for use with rounds ofammunition configured in accordance with the present invention has beenoffered from General Dynamics Corporation under propellant no. XPR 47C1.In view of the disclosures made herein, a skilled person will appreciatethat other propellants of suitable specification can be used in roundsof ammunition configured in accordance with the present invention.

During firing of the round of ammunition 100 within a weapon, thepropellant 124 in combination with the bullet 108 result in gas pressurecharacteristics and bullet-bore frictional characteristics that providefor subsonic flight of the bullet 108 and for sufficient gas pressurewithin a barrel bore of the weapon to cycling a gas-energized boltactuation mechanism of the weapon. For a given configuration ofammunition (e.g., 5.56 mm NATO ammunition), the bullet 108 will beheavier (e.g., by as much as 12 grains) than a bullet with a standardthickness drawn-metal jacket in view of the relatively thin jacket 120and greater volume of the core 118. When this relatively heavy,thin-jacket bullet 108 is subjected to the heat and pressure ofdischarge of the propellant 108, the relatively thin jacket 120 and therelatively large core 118 will result in enhanced obturation of thebearing surface portion 110 of the bullet 108 within the barrel bore ofthe weapon such that sliding friction between the bearing surfaceportion 110 and barrel bore will be enhanced relative to a comparablebullet of conventional (i.e., prior art) construction.

Sliding friction between the bore and the bullet 108 creates heat in thejacket 120. The lead of the core 118 has relatively low heatconductivity and the copper alloy of the jacket 120 has relatively highheat conductivity. Heat produced within the jacket 120 will penetratethe full thickness of the jacket 120 within the time it takes for thebullet 108 to pass down a length of the barrel bore of the weapon. Whenthis heat reaches the core 118, the core 118 serves as an effectiveinsulator thereby causing more heat to building the jacket 120 and,thus, soften the jacket 120 further to provide for more slidingfriction. Roughly speaking, given identical frictional heating, a jacketthat is three times as thick as a thinner jacket will heat up aboutone-third of the amount that the thinner jacket will heat up. Thefriction coefficient of copper is a strong function of the surfacehardness and hardness is a strong function of temperature. In thismanner, the jacket 120 being relatively thin further enhances slidingfriction between the bearing surface portion 110 and the barrel bore. Incombination with these frictional and obturation considerations of thebullet 108, the propellant 124 provides gas pressure characteristics(e.g., peak gas pressure, percent dwell around peak gas pressure, andaverage gas pressures) within the barrel bore of the weapon to generatesufficient gas-pressure derived energy at a gas port of the weapon forcycling its bolt carrier when the round of ammunition 100 is discharged.These gas pressure characteristics in combination with weight of thebullet 108 and frictional forces exerted on the bullet 108 causes thebullet 108 to decelerate from a supersonic speed (e.g., at a barrelposition where the gas port is located) to a subsonic speed prior toexiting the barrel bore.

It is disclosed herein that the use of a layer of friction reducingmaterial on the bearing surface portion 110 of the bullet 108 can beused to influence gas pressure characteristics and/or resulting velocityprofile of the bullet 108. For example, as disclosed above, molybdenumdisulfide is one example of a friction-reducing material composition towhich the jacket 120 and the shot (e.g., steel shot) can be exposedduring such shot peening for causing the exterior surface of the jacket120 to become coated with a layer of molybdenum disulfide. Coating thebearing surface portion 110 with a layer of molybdenum disulfide orother suitable friction reducing material composition can result in thebullet exhibiting reduced initial friction in the barrel bore, withdiminishing effect as velocity of the bullet 108 increases (e.g.,provides negligible effect with suitable velocity). Thus, itsapplication to the bearing surface portion 110 of the bullet 108 canresult in lower initial gas pressure, which moderates and broadens theinitial gas pressure spike produced by combustion of the propellant 120.In effect, such a layer of friction reducing material can delay onset ofheating of the jacket and thus influence sliding friction as a functionof time.

Referring now to FIGS. 3-5, various aspects of a round of ammunition 201configured in accordance with a second embodiment of the presentinvention for use with a barrel 203 of a rifle (i.e., a firearm) areshown. It is disclosed herein that the round of ammunition can beconstructed in a similar manner or the same manner as is described abovewith respect to the round to ammunition 100 discussed in reference toFIGS. 1 and 2. The round of ammunition 201 has a bullet 200 (i.e., aprojectile) engaged within a bullet receiving opening 205 of asmall-caliber cartridge casing 207 thereby forming apropellant-receiving cavity 209 within the small-caliber cartridgecasing 207. A propellant 211 is provided within the propellant-receivingcavity 209. The propellant 211 can be a relatively slow burning typepropellant that provides a rapid peak in pressure build up within thepropellant-receiving cavity 209 and that maintains a broader burnduration than relatively fast burning type propellants.

The bullet 200 includes a casing engaging segment 202, a rifling leademating segment 204, and a tip segment 206. The rifling leade matingsegment 204 has a frusto-conical shape tapering from a first diameter atits first end portion 208 to a second diameter at its second end portion210. Frusto-conical refers to a cone whose tip has been truncated by aplane parallel to its base. The rifling leade mating segment 204 extendsfrom a first end portion 212 of the casing engaging segment 202. The tipsegment 206 extends from the second end portion 210 of the rifling leademating segment 204. The first diameter is greater than the seconddiameter.

It is disclosed herein that the bullet 200 can be constructed and/ormanufactured in the same or similar manner as the bullet 108.Accordingly, the bullet 200 can be constructed of a drawn jacket with acore therein, can be constructed of a preformed core having a platedjacket, or any other suitably configured construction.

Preferably, but not necessarily, the tip segment 206 includes a barrelbore engaging portion 214 extending from the second end portion 210 ofthe rifling leade mating segment 204. The barrel bore engaging portion214 has a substantially cylindrical shape. A diameter of the barrel boreengaging portion 214 is substantially the same as the second diameter.The tip segment can also include a nose portion 215 having asubstantially hemi-spherical shape. However, a bullet configured inaccordance with the present invention is not limited to having a noseportion of any particular shape

A bullet in accordance with the present invention can be configured as a5.56 mm round of ammunition that is commonly used in a rifle such as anM4 carbine. Such a round of ammunition can be configured to have asecond diameter that is about 0.2 inches. In the case of such round ofammunition having a bullet configured in accordance with the bullet 200shown in FIGS. 4 and 5, the rifling leade mating segment of the bulletof that round of ammunition can have a conical taper CT, shown in FIG.4, of about 2.4 degrees and a rifling leade mating segment having alength of about 0.2 inches. In an embodiment specific to a standard asprovided by SAAMI, a rifling leade segment can have a conical taper ofabout 3.2 degrees. Accordingly, in view of the disclosures made herein,a skill ed person will understand that the present invention is directedto substantially or approximately mating the rifling leade segment of abullet to a rifling leade segment of a mating firearm's chamber and thatthe present invention is not unnecessarily limited to any particularconical taper of a rifling leade.

As shown in FIGS. 3 and 5, a rifling leade region 216 of the barrel 203preferably has substantially the same profile and dimensions as thebullet 200. Advantageously, such a mating interface between the riflingleade mating segment 204 of the bullet 200 and the rifling leade region216 of the barrel 203 limits a rate at which combustion gas can escapefrom a chamber 218 of the barrel 203 into its rifled bore 220. Forcartridges with relatively low average and/or peak combustion gaspressure (e.g., subsonic cartridges), limiting the rate at whichcombustion gas can escape from a chamber 218 of the barrel 203 into itsrifled bore 220 prior to the bullet 200 entering the rifled bore 220increases a magnitude of combustion gas pressure in the chamber 218 andsubsequently in the rifled bore 220 as the bullet 200 travels down therifled bore 220. In this manner, a higher level of combustion gaspressure is available to a gas-energized cartridge cycling mechanism ofthe rifle for enabling operation in semi-automatic and fully-automaticmodes of operation without a sound suppressor. In one such embodiment, abullet/rifling leade interface precludes or substantially inhibitscombustion gas from escaping from the, chamber 218 of the barrel 203into its rifled bore 220 prior to the bullet 200 entering the rifledbore 220. In contrast, in prior art implementations of bullet/riflingleade interfaces, the bullet has had a non-mating profile with respectto the rifling leade such that significant portions of combustion gaspressure is permitted to escape into the rifled bore of the barrel priorto the bullet entering the rifled bore of the barrel. As such, suchprior art bullet/rifling leade interfaces have lead to unreliable if notunacceptable firearm performance in semi-automatic and fully-automaticmodes of operation without a sound suppressor.

It is disclosed herein that configuring a round of ammunition inaccordance with the present invention can include manipulatingammunition-specific parameters including, but not limited to, jacketthickness, jacket material composition, jacket hardness, bearing surfacelength, core material composition, propellant type, propellant quantity,and jacket surface coating presence/type. All or a portion of theseammunition-specific parameters can be manipulated in view ofweapon-specific parameters including, but not limited to, barrel borediameter, barrel bore length, gas port position/size, required boltactuation mechanism energy, barrel bore material, etc. In view of thedisclosures made herein, a skilled person will be able to specifyammunition-specific parameters for ammunition configured in accordancewith the present invention for a particular configuration of weapon(e.g., a rifle) by experience and/or with minimal experimentation.

In the preceding detailed description, reference has been made to theaccompanying drawings that form a part hereof, and in which are shown byway of illustration specific embodiments in which the present inventionmay be practiced. These embodiments, and certain variants thereof, havebeen described in sufficient detail to enable those skilled in the artto practice embodiments of the present invention. It is to be understoodthat other suitable embodiments may be utilized and that logical,mechanical, chemical and electrical changes may be made withoutdeparting from the spirit or scope of such inventive disclosures. Toavoid unnecessary detail, the description omits certain informationknown to those skilled in the art. The preceding detailed descriptionis, therefore, not intended to be limited to the specific forms setforth herein, but on the contrary, it is intended to cover suchalternatives, modifications, and equivalents, as can be reasonablyincluded within the spirit and scope of the appended claims.

1. A bullet, comprising: a casing engaging segment; a rifling leademating segment extending from a first end portion of the casing engagingsegment, wherein the rifling leade mating segment has a frusto-conicalshape tapering from a first diameter at a first end portion thereof to asecond diameter at a second end portion thereof and wherein the firstdiameter is greater than the second diameter; and a tip segmentextending from the second end portion of the rifling leade matingsegment.
 2. The bullet of claim 1 wherein: the tip segment includes abarrel bore engaging portion extending from the second end portion ofthe rifling leade mating segment; and the barrel bore engaging portionhaving a substantially cylindrical shape.
 3. The bullet of claim 2wherein a diameter of the barrel bore engaging portion is substantiallythe same as the second diameter.
 4. The bullet of claim 2 wherein: thetip segment includes a nose portion and a barrel bore engaging portionextending between the tip portion and the second end portion of therifling leade mating segment; the barrel bore engaging portion has asubstantially cylindrical shape; and the nose portion has asubstantially hemi-spherical shape.
 5. The bullet of claim 4 wherein adiameter of the barrel bore engaging portion is substantially the sameas the second diameter.
 6. The bullet of claim 1 wherein the riflingleade mating segment has a conical taper of between about 2.4 degreesand 3.2 degrees.
 7. The bullet of claim 6 wherein: the rifling leademating segment has a length of about 0.2 inches; and the second diameteris about 0.2 inches.
 8. A bullet, comprising: a jacket drawn from acopper alloy material, wherein the jacket has a casing engaging segment,a rifling leade mating segment, and a tip segment, wherein the riflingleade mating segment linearly tapers from a first diameter at a firstend portion thereof to a second diameter at a second end portionthereof, wherein the rifling leade mating segment extends from the firstend portion of the casing engaging segment, wherein the tip segmentextends from the second end portion of the rifling leade mating segment,wherein the first diameter is greater than the second diameter, whereinthe casing engagement segment defines a bearing surface portion of thejacket, wherein the bearing surface portion has a nominal thickness lessthan about 0.010″, and wherein the copper alloy material of at least thebearing surface portion of the jacket has a nominal hardness that issubstantially greater than an as-drawn hardness of the copper alloymaterial of the bearing surface portion of the jacket; and a lead coreprovided within the jacket
 9. The bullet of claim 8 wherein: the tipsegment includes a barrel bore engaging portion extending from thesecond end portion of the rifling leade mating segment; the barrel boreengaging portion having a substantially cylindrical shape; and adiameter of the barrel bore engaging portion is substantially the sameas the second diameter.
 10. The bullet of claim 9 wherein: the tipsegment includes a nose portion and a barrel bore engaging portionextending between the tip portion and the second end portion of therifling leade mating segment; the barrel bore engaging portion has asubstantially cylindrical shape; and the nose portion has asubstantially hemi-spherical shape.
 11. The bullet of claim 10 wherein:the rifling leade mating segment has a taper of between about 2.4degrees and 3.2 degrees
 12. The bullet of claim 8 wherein the bearingsurface portion of the jacket is at least partially coated with afriction-reducing material composition.
 13. The bullet of claim 12wherein the friction-reducing material composition is molybdenumdisulfide.
 14. The bullet of claim 13 wherein the bearing surfaceportion is coated in its entirety with the friction-reducing materialcomposition.
 15. The bullet of claim 8 wherein: the nominal hardness ofthe copper alloy material of at least bearing surface portioncorresponds to a tensile strength of between about 32 ksi and about 44ksi; the bearing surface portion of the jacket is at least partiallycoated with a friction-reducing material composition; and the bearingsurface portion of the jacket has a thickness between about 0.004″ andabout 0.008″.
 16. A round of ammunition configured for providingsufficient energy for cycling a bolt carrier in a rifle having agas-energized bolt carrier actuation mechanism, comprising: asmall-caliber cartridge casing configured in accordance with an originalequipment manufacturer (OEM) specification for the rifle; a bullethaving a casing engaging segment, a rifling leade mating segment, and atip segment, wherein the rifling leade mating segment has afrusto-conical shape tapering from a first diameter at a first endportion thereof to a second diameter at a second end portion thereof,wherein the rifling leade mating segment extends from the first endportion of the casing engaging segment, wherein the tip segment extendsfrom the second end portion of the rifling leade mating segment, whereinthe first diameter is greater than the second diameter, wherein thecasing engagement segment defines a bearing surface portion of thebullet engaged within a bullet receiving opening of the small-calibercartridge casing thereby forming a propellant-receiving cavity withinthe small-caliber cartridge casing; and a propellant within thepropellant-receiving cavity of the small-caliber cartridge casing,wherein the propellant is configured by a manufacturer thereof for beingused in medium caliber ammunition.
 17. The round of ammunition of claim16 wherein: the bullet has a core made of a metal having lead as itsmajor constituent component and a jacket drawn from metal having copperas its major constituent component; the bearing surface portion has anominal thickness less than about 0.010″; and the copper alloy materialof at least the bearing surface portion of the jacket has a nominalhardness that is substantially greater than an as-drawn hardness of thecopper alloy material of the bearing surface portion of the jacket 18.The round of ammunition of claim 16 wherein: the bullet has a core madeof a metal having lead as its major constituent component and a jacketdrawn from metal having copper as its major constituent component; anominal thickness of the jacket is less than about 0.010″; and at leastthe bearing surface portion of the jacket has a nominal hardness that issubstantially greater than an as-drawn hardness of the jacket.
 19. Theround of ammunition of claim 16 wherein: the tip segment includes abarrel bore engaging portion extending from the second end portion ofthe rifling leade mating segment; the barrel bore engaging portionhaving a substantially cylindrical shape; and a diameter of the barrelbore engaging portion is substantially the same as the second diameter.20. The round of ammunition of claim 16 wherein: the nominal hardness ofthe copper alloy material of at least bearing surface portioncorresponds to a tensile strength of between about 32 ksi and about 44ksi; the bearing surface portion of the jacket is at least partiallycoated with a friction-reducing material composition; and the bearingsurface portion of the jacket has a thickness between about 0.004″ andabout 0.008″.